I used these in October. You can buy them at the counter service resturants while in line. If I remember correctly, it's actually a two step process as you have to buy the ticket and then redeem the ticket in two separate transaction.
The way we figure it is if you were probably going to get a drink and a snack anyway, it's a good deal. Since my DH is addicted the the tollhouse ice cream sandwiches, the snack is pretty much a given with us.